In an original digital subscriber line (DSL) system, bit errors of data in a line often occur because of influence of impulse noises. In order to ensure the stability of a DSL system, an impulse noise protection (INP, Impulse noise protection) technology is developed. The INP technology mainly uses an error correcting code to correct bit errors generated in sent data, for example, a coding gain additionally provided by Reed-Solomon (RS, Reed-Solomon) codes is used to reduce the influence of the impulse noises, thus increasing the stability of the DSL system. However, with the increasing of a bandwidth and the increasing of a rate, if an original RS coding scheme is still used, an RS code word with many check bytes (that is, redundancy) and shorter length needs to be used. In this case, a net gain of the RS code changes into a negative value, which is not conducive to the increase of the rate, and the INP protection provided by the system cannot deal with the influence of a super long impulse noise.
In order to better deal with the influence of the super long impulse noise on an xDSL system, a physical layer retransmission scheme is developed. The current retransmission scheme includes retransmission mechanisms of a transport protocol specific transmission convergence layer (TPS-TC, Transport Protocol Specific Transmission Convergence Layer), a physical media-specific transmission convergence layer (PMS-TC, Physical Media-Specific Transmission Convergence Layer), and a physical media dependent layer (PMD, Physical Media Dependent Layer). The retransmission scheme can re-send the data damaged by the impulse noise, thus reducing a bit error rate in the line and increasing the service stability.
During the research and implementation of the prior art, the inventor of the present invention finds that: the retransmission scheme alleviates the influence of the super long impulse noise on the system to a certain extent and improves the service stability of the system, but meanwhile, incurs a long delay (Delay). For example, in a retransmission system located on the PMS-TC layer, an additionally incurred delay is longer than about 10 ms, and a maximum data delay is even longer than 20 ms. This delay has little influence on a service having a high requirement on the bit error rate and a low requirement on the delay. However, for a service having a low requirement on the bit error rate and a high requirement on the delay, the quality of experience (QoE, Quality of experience) of a user is greatly deteriorated.